1. Field
Aspects of the present disclosure relate generally to wireless communication, and more particularly, to methods and apparatus for rejecting unreliable downlink (DL) transmit power control (TPC) commands based on signal-to-interference-ratio estimates.
2. Background
Wireless communication networks are widely deployed to provide various communication services such as telephony, video, data, messaging, broadcasts, and so on. Such networks, which are usually multiple access networks, support communications for multiple users by sharing the available network resources. One example of such a network is the UMTS Terrestrial Radio Access Network (UTRAN). The UTRAN is the radio access network (RAN) defined as a part of the Universal Mobile Telecommunications System (UMTS), a third generation (3G) mobile phone technology supported by the 3rd Generation Partnership Project (3GPP). The UMTS, which is the successor to Global System for Mobile Communications (GSM) technologies, currently supports various air interface standards, such as Wideband-Code Division Multiple Access (W-CDMA), Time Division-Code Division Multiple Access (TD-CDMA), and Time Division-Synchronous Code Division Multiple Access (TD-SCDMA). The UMTS also supports enhanced 3G data communications protocols, such as High Speed Packet Access (HSPA), which provides higher data transfer speeds and capacity to associated UMTS networks.
In a typical wireless communication environment, RF signal transmissions between a base station (e.g., NodeB in UMTS) and user equipment (UE) are subject to degradation, such as path loss, shadow fading and multipath, which is typically caused by such factors as terrain contours (e.g., mountains, forests), environment (e.g., urban or rural), propagation medium (dry or moist air), changes in distance between a base stations and a mobile UE, etc. Due to the signal degradation, transmit power of the UE may be too low, which may cause dropped calls or failed data transmissions. The UE's transmit power is typically controlled by the downlink (DL) Transmit Power Control (TPC) commands that are sent from NodeB to UE through downlink (DL) Dedicated Physical Control Channel (DPCCH). UE decodes these DLTPC bits (either 0/Down or 1/Up) and adjusts its transmit power accordingly. However, the transmit power may be improperly adjusted due to DLTPC decoding errors when the signal quality on the DL channel is poor. In other words, for DLTPC signals having very low Signal-to-Interference-Ratio Estimate (SIRE), the DLTPC decode reliability degrades significantly, which may cause incorrect adjustment in UE's transmitter power. Therefore, there is need for a mechanism for rejecting unreliable DLTPC commands.